Remediation of peruvian Acid Mine Drainage by Biohydrometallurgical Processes

The main aim was to demonstrate the technical feasibility of the remediation processes by electrowinning and bioprecipitation, for toxic metals removal from acid mine drainage (AMD) coming from a zinc mine located in Tùnel Kingsmill outlet of the Rio Yaulì (district of Yauli - Perù). The study consists in a preliminary work: the experimental tests have been conducted by synthetic solutions. Electrowinning tests have been carried out after chemical iron-aluminum precipitation, that permitted a complete Fe-Al removal. By electrochemical experiments, high metals removal, with a low energetic consumption, has been achieved: in particular, by Zn and Mn electrodeposition, it was possible to achieve 80-90% Zn and Mn removal, with a low energetic consumption. The culture of sulphate-reducing bacteria (SRB) of genera Desulfovibrio sp. was used for the bioprecipitation tests. The treatment of AMD by SRB is based on the ability of SRB to reduce sulphates to hydrogen sulphide, which binds readily with metals to form sparingly soluble precipitates. The kinetic of the selective precipitation of Fe, Zn, Al and Cu has been investigated. This method has been performed in two interconnected reactors. Achieved results demonstrate the 98-99% elimination of Cu by bacterially produced H2S.